I have no idea what this plate is, Could somebody help?

It only has a mark on the bottom that says No 3155 on top of what it looks like an “h”

I’ll try to insert pictures or at least a link to the pictures

Thanks

[url=http://www.flickr.com/photos/116734165@N07/12488779643/in/photostream/]Bottom[/url]

[url=http://www.flickr.com/photos/116734165@N07/12488656125/in/photostream/]Top[/url]